CLEAR COVER FOR DIFFERENT R.C.C. MEMBERS

What Is Clear Cover (or) Cover in Concrete?

The clear cover (or) Cover in RCC, is the distance between the exposed concrete surface (without plaster and other finishes) to the nearest surface of the reinforcement bar i.e., Steel rod.

Mostly, it is known as "clear cover" or "minimum concrete cover" in general terms on a construction site.

Why clear cover is important?

Cover is provided to protect the reinforcing bar (rebar) from corrosion due to weather and fire. If we don't leave a cover, then the reinforcing bar will stick to the surface of the shuttering and cause rust in the bar after we casting the column or beam and also damage the strength of the column or beam.

For example, in the case of fire in a building, the metal begins to melt and lose its strength. Therefore, the clear cover acts as an insulator and prevents from melting.

This gives more strength to the bars, reduces the chances of slipping and also increases the durability of the bars. This provides adequate embedding for the reinforcing bars to withstand stress without loss of grip.

How to Define Nominal Cover

As per IS 456(Clause 26.4.1), the term clear cover has been replaced by the term Nominal cover.

The nominal cover is the distance between the exposed concrete surface to nearest reinforcement bar ( it can be any bar I.e., main bar, longitudinal bar and even links or stirrups).

What Is Effective Cover in Concrete?

The Effective cover is the distance measured betweenthe exposed concrete surface (without plaster and other finishes) to the centre of the area ( centroid ) of reinforcement, i.e., tension or compression reinforcement. 

Effective cover = overall depth – effective depth.    (Or). 

Effective cover = Clear cover + Diameter of Stirrup + (Diameter of main reinforcement bar ÷ 2).

Member	Clear cover (Normal Conditions)	wet climatic environment or sea side location
Foundation	75 mm
Raft Foundation	Top = 50 mm Bottom = 75 mm Sides = 75 mm
Strap Beam	50 mm
Beam	25 mm	35 to 40 mm
Column	40 mm	50 mm
Flat Slab	20 mm
Slab	15 mm

STANDARD CONVERSION FACTORS USED IN CONSTRUCTION FIELD

          A civil engineer on site must learn some basic conversions. Here we are provided some basic measurements and conversion factors which are generally used on site. Hope it will help you in work.

Units	Conversion Factor
1 meter	3.28 Feet
1 meter	39.37 inches = 1.09 Yards
1 meter	100 cm
1 meter	1000 mm
1 foot	12 inches
1 inch	2.54 cm = 25.4 mm
1 chadaram	100 sq feet
1 inch	8 soot

 

Units	Conversion Factor
1 Bag of cement	0.0347 cum
1 Sq m	10.76 sq ft
1 acre	43560 sq. ft = 4046.46 sqm
1 ltr	0.22 Gal
1 gallon	4.546 ltr
1 cu ft	28.317 ltr
1 cu ft	0.028 cu mtr
1 cu ft	6.24 gallons

 

UNIT WEIGHT OF STEEL BAR PER METER

Diameter of bar	Weight (kg/m)	Weight (kg/ft)
6 mm	0.22 kg/m	0.068 kg/ft
8 mm	0.395 kg/m	0.12 kg/ft
10 mm	0.616 kg/m	0.19 kg/ft
12 mm	0.88 kg/m	0.27 kg/ft
16 mm	1.578 kg/m	0.48 kg/ft
20 mm	2.466 kg/m	0.75 kg/ft
25 mm	3.853 kg/m	1.172 kg/ft

 By using the formula D²/162 we calculate the unit weight of steel bar per meter

 By using the formula D²/533 we calculate the unit weight of steel bar per meter

Note:

Length of TMT Steel rod will be 12 meter (or) 40 feet.

What Is Unit Weight?

Unit weight of any substance is defined as the ratio of mass or weight per unit volume. It is usually measured in gm/cm, lb/ft,  or, kg/cm or kg/m etc.

The unit weight of materials varies depending on their composition & properties of ingredients. It gives an idea about the weight or lightness of the materials.

What Is Unit Weight of Steel?

The density of steel is around 7850 kg/m³ (or) 7.85 g/cm³ (or) 490 lbs/ft³ (or) 13231 lbs/yd³.

The various steel diameters used in construction are 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 32 mm and 40 mm.

The Formula Used To Calculate Weight of Steel

The formula used to calculate the unit weight of steel bars is D²/162.                 Where, D = Diameter of steel bars, 162 is a constant value.

Derivation of formula for calculating unit weight of steel